Introduction

PHP supports the direct io functions as described in the Posix
Standard (Section 6) for performing I/O functions at a lower
level than the C-Language stream I/O functions
(fopen(), fread(),..). The use
of the DIO functions should be considered only when direct
control of a device is needed. In all other cases, the standard
filesystem functions are more
than adequate.

Note:

This extension has been moved to the
» PECL repository and is no longer bundled with
PHP as of PHP 5.1.0.